Incandescent light bulbs are a source of electric light that creates light by running electricity through a resistive filament, thereby heating the filament to a very high temperature, so that it glows and produces visible light. Incandescent bulbs are made in a wide range of sizes and voltages, from 1.5 volts to about 300 volts. The bulbs consist of a generally glass or plastic enclosure with a filament of tungsten wire inside the bulb through which an electrical current is passed. Incandescent lamps are designed as direct “plug-in” components that mate with a lamp holder via a threaded Edison base connector (sometimes referred to as an “Edison base” in the context of an incandescent light bulb), a bayonet-type base connector (i.e., bayonet base in the case of an incandescent light bulb), or other standard base connector to receive standard electrical power (e.g., 120 volts A.C., 60 Hz in the United States, or 230V A.C., 50 Hz in Europe, or 12 or 24 or other D.C. voltage). The base provides electrical connections to the filament. Usually a stem or glass mount anchors to the base, allowing the electrical contacts to run through the envelope without gas or air leaks.
Incandescent light bulbs are widely used in household and commercial lighting, for portable lighting, such as table lamps, car headlamps, flashlights, and for decorative and advertising lighting. However, incandescent light bulbs are generally inefficient in terms of energy use and are subject to frequent replacement due to their limited lifetime (about 1,000 hours). Approximately 90% of the energy input is emitted as heat. These lamps are gradually being replaced by other, more efficient types of electric light such as fluorescent lamps, high-intensity discharge lamps, light emitting diodes (LEDs), etc. For the same energy input, these technologies give more visible light and generate much less heat. Particularly, LEDs consume a fraction of the energy used to illuminate incandescent bulbs and have a much longer lifetime (e.g. 50,000 to 75,000 hours). Furthermore, LED light sources are a very clean “green” light source and also provide good color reproduction.
LED light bulbs are far more efficient than traditional incandescent lamps, most notably because they use only a small fraction of the electricity of an incandescent. As traditional incandescent bulbs continue to be phased out, LED has become the mainstream light sources used on a variety of indoor and outdoor lighting fixtures. However, traditional LED light bulbs are not without its disadvantages, for example, the complicated designs which incorporate the heavy aluminum heat sinks and an electronic circuit for power conversion. Consequently, the cost is high and the shape is somewhat strange compared with the elegant incandescent bulbs people are accustomed to.
An LED filament bulb is a light bulb that uses LEDs as its filaments. Accordingly, it is desirable to provide a novel LED filament light bulb with improved performance and aesthetics that may be used as a better replacement for a typical incandescent light bulb than traditional LED light bulbs.
The LED has advantages of environmental protection, energy saving, high efficiency and long lifespan, and therefore it attracts widespread attention in recent years and gradually replaces traditional lighting lamps. However, due that the luminescence of the LED has directivity, current LED lamps is unable to provide with an illumination with a wide angle range like traditional lamps. Accordingly, how to design LED lamps with similar wide range of illumination to the traditional lamps challenges the industries.
Recently, an LED light bulb has been provided and gradually replaces the use of incandescent light bulbs. The kind of the LED light bulbs is provided with multiple LED filaments due to the limited illuminating angle of LED light sources. The LED filaments are aligned in a circle in the LED light bulb, and each of the LED filaments faces different angles for illumination, such that the illuminating angle of the LED light bulb could be increased in general. The manufacturing process of the LED filament includes: fixing multiple LED chips in series to a long, narrow glass substrate, enclosing the whole glass substrate by silicone gel mixed with phosphor powders, and processing electrical connection of the LED filament. When the LED filaments are welded to a stand in the LED light bulb, the LED filaments have to be welded one by one, which is numerous and complicated. Further, the LED filaments are welded in a spot welding manner, which requires high standard regarding property and size of materials, and has a risk of faulty welded joint. In appearance, the LED filaments are hard and straight and lack flexibility and variation. The conventional LED light bulb gives people nothing more than a visually stiff feeling and cannot provide an aesthetic appearance.
In addition, the color temperature of light generated by the LED filaments is usually too high such that the use of the LED filaments is only suitable for limited environments. In a comfort and relax occasion, using conventional tungsten filament bulbs with low color temperature of light for illumination is much better.
Further, the LED filaments generate a large amount of heat during operation. Heat may damage components in the LED light bulb such as LED chips and a driving circuit and lower the efficiency of the LED filaments.